1. Field of the Invention
The present application is related to electronic cameras and more particularly, to electronic cameras with autofocus and/or zoom, and particularly having optical and electrical integration of autofocus and/or zoom components.
2. Description of the Related Art
If the position of an optical train of a camera is fixed relative to the position of the image sensor, the resulting electronic camera is said to be fixed focus. Rigidly fixing the optical system in place means only objects that are a certain distance from the camera will be in focus on the image sensor. Fixed focus cameras have advantages in terms of smallness of physical dimensions and cost, but the performance is limited. In particular, the focus distance is often set at 1.2 m so that objects from 60 cm to infinity appear tolerably sharp. However, the image sharpness is not especially good and objects that are closer to the camera than 60 cm will be blurred.
While it is possible to set the focus at a closer distance to correct for this problem, this means that the sharpness of distant objects declines in compensation. A characteristic that is common to both conventional fixed and auto focus cameras is that the area that can be viewed, known as the field of view of the camera, is determined by the optical design and the dimensions of the image sensor and cannot be changed. For convenience, field of view is often described as the equivalent solid angle in the horizontal, vertical or diagonal plane.
Cropping an image to reduce the field of view has advantages that it entails no moving parts, can be performed almost instantaneously and involves very low power and physical space to implement. It is a relatively low cost method of changing the field of view. However cropping involves the loss of information. That is, to restrict the field of view, an image is cropped to, say, one quarter of its original area, such that three quarters of the image is discarded. Consequently, a cropped image can often have inferior quality to both the original image and a mechanical zoom image of the same field of view.
Generally, the lower the quality of the optical train, the larger the PSF or point spread function will be. In many conventional cameras, the optical train tends to be underspecified, such that points of captured light spread excessively to cover several pixels resulting in blurred images.
Lenses may be assembled in a lens turret to form an optical train. In a conventional method, a lens turret may be fabricated first, after which the lenses may be inserted, and then fixed in a desired location inside the lens turret. Methods of enhanced precision are desired.